The present invention relates to an inhaler for delivery of a medicament by inhalation and in particular to the actuation mechanism used in the inhaler used to actuate the canister to deliver a dose of medicament.
Known inhalers hold a canister of medicament which is actuatable by compression to deliver a dose of medicament Many known inhalers have been designed with an actuation mechanism to automatically actuate the canister. The present invention is concerned with optimising such an actuation mechanism.
Some known actuation mechanisms are breath-actuated, so that they operate in response to inhalation by a user. Typically, a breath-actuated inhaler includes a pre-loading mechanism for loading a resilient loading element with an actuation force which is used to bias compression of the canister, in combination with a triggering mechanism arranged to hold the resilient loading element against compression of the canister and thereby store the actuation force. When delivery of a dose is required, the triggering mechanism releases to allow compression of the canister in response to inhalation by the user.
A problem often encountered, especially by elderly, young or infirm users, is that it is difficult to generate enough force to load the actuation mechanism, for example the resilient loading element if a pre-loading mechanism is provided. Clearly the energy provided must be at least that needed to actuate the canister and in fact the provision of an actuation mechanism means that additional energy must be applied as there will inevitably be energy wastage in any mechanism. The first aspect of the present invention is intended to assist in loading of the pre-loading mechanism.
One solution to this problem would be to provide a dispenser where the force required to actuate the canister is generated by an electric motor, but that suffers from the serious disadvantage that the inhaler ceases to operate when the motor power supply runs out. This is highly undesirable in the dispensing of medicaments.
According to the present invention, there is provided an inhaler for delivery of a medicament by inhalation, comprising:
a housing for holding a canister of medicament having a generally cylindrical body and a valve stem with the cylindrical axis of the body in a predetermined direction, the body and valve stem being compressed together to actuate the canister to deliver a dose of medicament from the valve stem;
an actuation mechanism arranged to receive energy for compressing the canister by manual depression of two contact members movable relative to the housing and disposed opposite one another on either side of the axis of a canister held in the housing.
By providing the contact members opposite one another on either side of the axis of the canister, the inhaler becomes far easier to load. The inhaler may be held in the palm of one hand and the two contact members depressed by a finger and thumb which allows the force to be easily applied. The inhaler may even be laid on a surface such as a table with one contact member touching the surface and the opposite contact member raised upwardly to allow the user to apply force by leaning on the inhaler and/or using both hands.
Preferably, the distance between the extremities of the contact members before depression is less than the maximum length of the inhaler in a direction parallel to the axis of canister held in the housing or is less than the overall length of the canister including the body and the valve stem. Many known inhalers are arranged to load the resilient loading element by application of force along the axis of the canister, in which case there is a long distance between the parts which must be relatively moved, typically the length of the inhaler in a direction parallel to the axis of the canister and is longer than the overall length of the canister. This hinders the application of force because it is difficult to grip both contact surfaces especially for a person having relatively small hands. In contrast the present invention allows the movable parts to be closer together and hence more easily manipulated. The distance between the extremities of the buttons may be less than 95%, 90%, 85%, 80% or preferably 75% of the overall length of the canister. valve stem of the canister are relatively compressed to actuate the canister. By providing such gearing within the actuation mechanism, the size of the force which must be applied to the contact members may be reduced as compared to a system applying force over the distance by which the canister is compressed, because the energy required to be stored is the same in both cases. Desirably, the total distance over which the two contact members move is 2 times, 3 times, 5 times or preferably 8 or 10 times the canister compression distance
A breath-actuated inhaler is typically stored in a loaded state in which the resilient loading element stores the actuation force. It is therefore the intention of the second aspect of the invention to provide a triggering mechanism which resist accidental operation.
According to a second aspect of the present invention, there is provided a breath-actuated inhaler for delivery of a medicament by inhalation, comprising:
a housing defining a mouthpiece and arranged to hold a canister of medicament actuatable to deliver a dose of medicament;
an actuation mechanism arranged to be operated to actuate the canister and including a pivotably mounted trigger vane arranged to be moved by inhalation at the mouthpiece to cause operation of the actuation mechanism, wherein the trigger vane is mounted to pivot about an axis passing through the center of mass of the trigger.
Such an arrangement of the triggering mechanism reduces the chance of accidental triggering due to a shock, for example if the inhaler is dropped. Any forces applied to the inhaler act on the trigger vane through the pivot, but in the present invention this does not create any torque tending to pivot the trigger vane because the pivot is also the center of mass.
A convenient structure for the trigger vane is to constitute it by a vane portion extending outwardly from the axis of the trigger vane to be moved by an air flow created by inhalation at the mouthpiece and a counterweight portion disposed on the opposite side of the axis of the trigger vane from the vane portion.
Whilst accidental triggering is undesirable, it is critical that a breath-actuated inhaler never fails when the user inhales. This is particularly important in an emergency where delivery of the medicament could be critical to the health or even the life of the user. The force provided by inhalation is relatively small compared to the force required to actuate the canister, so it is a difficult technical problem to devise a structure for the triggering mechanism which safely holds the stored actuation force without tending to trigger accidentally, whilst ensuring that triggering does occur when inhalation actually occurs. The third aspect of the present invention is intended to meet this design requirement. It would also be desirable to provide a triggering mechanism which achieves this balance with a large tolerance window for manufacturing the components of the triggering mechanism.
According to a third aspect of the present invention there is provided a breath-actuated inhaler for delivery of a medicament by inhalation, comprising
a housing having a mouthpiece and arranged to hold a canister of medicament actuatable to deliver a dose of medicament from the mouthpiece by compression of the canister, and
an actuation mechanism for actuating the canister, comprising:
a pre-loading mechanism for loading a resilient loading element with an actuation force, the resilient loading being element being arranged when loaded to bias compression of the canister,
a triggering mechanism comprising a knee joint having a locked position where the knee joint holds the resilient loading element against compression of the canister and a trigger responsive to the inhalation at the mouthpiece to break the knee joint into a broken position where the knee joint releases the resilient loading element to allow compression of the canister,
wherein the trigger comprises a second knee joint connected to the first mentioned knee joint and having a locked position where the second knee joint holds the first knee joint in its locked position and movable in response to inhalation at the mouthpiece to a broken position to break the first knee joint.
Such use of two knee joints connected together in such a ganged relationship has been found to meet the design requirement discussed above of ensuring triggering upon inhalation whilst limiting the chances of accidental triggering. In particular, the first knee joint is safely held against accidental triggering by the second knee joint in the locked state but the pair of knee joint respond positively to inhalation by the user to release the triggering mechanism and actuate the cannister. This effect may be achieved within comparatively relaxed tolerances for the parts of the mechanism. This ensures that the inhaler delivers a dose or inhalation, even if the parts form over time.
Preferably the second knee joint has a plurality of jointed links, at least one of which is a trigger vane movable by inhalation at the mouthpiece. This allows the triggering mechanism to respond actively to inhalation.
Desirably the pre-loading mechanism further comprises a pivotable lever biased by the resilient loading element to compress the cylinder through a portion coupled to the canister, the first knee joint being connected to the lever A for holding the resilient biasing element. Use of a lever to compress the cannister allows leverage to be obtained between the compressional force on the cannister, the resilient biasing element and the locking mechanism. This assists in allowing the forces within the pre-loading mechanism to be controlled by the triggering mechanism, thereby enhancing the effect of triggering mechanism.
Advantageously, the first knee joint is connected to the lever at a position further away from the pivot of the lever than the portion through which the lever is coupled the canister.
Advantageously, the resilient loading element biases the lever at a position further away from the pivot than the portion through which the lever is coupled to the canister.